START: Get down on your hands and knees with your palms flat on the floor and shoulder-width apart. Your knees should be bent 90 degrees and your thighs should be perpendicular to the floor. You knees should be hip-width apart.

MOVEMENT: Brace your abs, and raise your right arm and left leg until they are in line with your body. Hold for 5 to 10 seconds. Return to the starting position. Repeat with your left arm and right leg. Try to keep your hips and lower back still, even as you switch arms and legs. Continue to alternate back and forth.